1. Field of the Invention
The present invention relates to a lens barrel including a focusing mechanism capable of performing an automatic focusing operation and a manual focusing operation without performing mechanical switching of an automatic focusing mechanism and a manual focusing mechanism.
2. Description of the Related Art
Conventionally, in lens barrels which are applied to photographing apparatuses (cameras) and the like which perform photographing or the like, a lens barrel configured to be usable with an AF operation and an MF operation being properly switched by an automatic focusing (autofocus, hereinafter called AF) mechanism and a manual focusing (manual focus, hereinafter called MF) mechanism being mechanically switched has been put into practice in general.
In the focusing mechanisms in the conventional lens barrels, some of the focusing mechanisms are each configured to perform an AF operation by using, for example, a lead screw provided at a drive shaft of a drive motor and to be able to perform an MF operation by a drive force from a manual operation member by providing a clutch mechanism in a drive force transmitting mechanism which transmits a drive force from the drive motor, and shutting off the transmission of the drive force from the drive motor by the clutch mechanism at the time of the MF operation.
Further, in the lens barrels which perform AF operations by using ultrasound motors, various proposals each about a so-called fulltime AF/MF mechanism which is configured to be able to perform an AF operation and an MF operation without switching by a motor and a differential mechanism are made by, for example, Japanese Patent Application Laid-Open Publication No 1-167715 and the like, and are also generally put into practice.
Incidentally, in photographing apparatuses (cameras), so-called digital cameras and the like which acquire electronic images by using image pickup devices have entered widespread use. In each of the lens barrels which are applied to this kind of cameras and the like, such a focusing mechanism is often used that makes a rotational shaft of a stepping motor a lead screw, and moves a nut which is screwed onto the lead screw in the optical axis direction, thereby advancing and retracting a lens for focusing (focusing lens) in the optical axis direction, in order to realize noise reduction due to adaptation to an imager Af operation and adaptation to moving image photographing.